1. Field of the Invention
This invention relates in general to gas discharge lighting devices of flat form configuration. More particularly, the invention relates to the construction and method of operation of gas discharge lighting devices made in flat glass envelopes to produce illuminated graphic patterns in signs, architectural lighting or other graphic displays.
2. Description of the Prior Art
Lighted signs of Neon or Mercury vapor UV discharge phosphor coated types are in common use. The predominant construction of this type of lighted signs is through the use of bent tubing. In U.S. Pat. No. 2,102,049 to Warren, a method of constructing Neon signs using molded glass in flat arrays is described.
The Neon tube sign is well applied to large signs or architectural lighting. For small, detailed graphic signs, tubing has the disadvantage of limiting the graphic design because of the constant diameter tubes, because it is very difficult to get multi-colored patterns in one discharge path, and because the cost to make many signs of the same design is very expensive.
In the Warren U.S. Pat. No. 2,102,049, only the use of Neon or other colored gases is discussed. Also, the envelope construction in that patent only includes channels of constant width and uniform height, and requires a continuous discharge path from one end electrode to the other end electrode. All of this limits the graphic possibilities for this type of sign construction.
The prior art also includes flat envelope graphic signs that are made from thick glass plates. The plates have channels created by removing glass abrasively or by other methods, and a flat glass plate is then fused to the channel plate. Signs of this construction can have various width discharge channels, but the viewing surface of the sign is flat and there is no possibility for contour or surface texture, which are important aesthetic factors in graphic and sign design.